Application of an In Vitro Psoriatic Skin Model to Study Cutaneous Metabolization of Tazarotene

Formulation development of tazarotene-loaded PLGA nanoparticles for follicular delivery in the treatment of inflammatory skin diseases

Tazarotene is a widely prescribed topical retinoid for acne vulgaris and plaque psoriasis and is associated with skin irritation, dryness, flaking, and photosensitivity. In vitro permeation of tazarotene was studied across the dermatomed human and full-thickness porcine skin. The conversion of tazarotene to the active form tazarotenic acid was studied in various skin models. Tazarotene-loaded PLGA nanoparticles were prepared using the nanoprecipitation technique to target skin and hair follicles effectively. The effect of formulation and processing variables on nanoparticle properties, such as particle size and drug loading, was investigated. The optimized nanoparticle batches with particle size <500 µm were characterized further for FT-IR analysis, which indicated no interactions between tazarotene and PLGA. Scanning electron microscopy analysis showed uniform, spherical, and non-agglomerated nanoparticles. In vitro release study using a dialysis membrane indicated a sustained release of 40-70 % for different batches over 36 h, following a diffusion-based release mechanism based on the Higuchi model. In vitro permeation testing (IVPT) in full-thickness porcine skin showed significantly enhanced follicular and skin delivery from nanoparticles compared to solution. The presence of tazarotenic acid in the skin from tazarotene nanoparticles indicated the effectiveness of nanoparticle formulations in retaining bioconversion ability and targeting follicular delivery.

Challenges in Psoriasis Research: A Systematic Review of Preclinical Models

INTRODUCTION

Psoriasis is a chronic inflammatory skin disease with variable clinical presentation, multifactorial etiology and an immunogenetic basis. Several studies demonstrate that it results from a dysregulated interaction between skin keratinocytes, immune cells, and the environment that leads to a persistent inflammatory process modulated by cytokines and T cells. The development of new treatment options requires increased understanding of pathogenesis. However, the successful implementation of effective drugs requires well-characterized and highly available preclinical models that allow researchers to quickly and reproducibly determine their safety and efficacy.

METHODS

A systematic search on PubMed and Scopus databases was performed and assessed to find appropriate articles about psoriasis models applying the key words previously defined. The PRISMA guidelines were employed.

RESULTS

A total of 45 original articles were selected that met the selection criteria. Among these, there are articles on in vivo, in vitro, and ex vivo models, with the in vitro model being the majority due to its ease of use. Within animal models, the most widely used in recent years are chemically induced models using a compound known as imiquimod. However, the rest of the animal models used throughout the disease's research were also discussed. On the other hand, in vitro models were divided into two and three dimensions. The latter were the most used due to their similarity to human skin. Lastly, the ex vivo models were discussed, although they were the least used due to their difficulty in obtaining them.

CONCLUSIONS

Therefore, this review summarizes the current preclinical models (in vivo, in vitro, and ex vivo), discussing how to develop them, their advantages, limitations, and applications. There are many challenges to improve the development of the different models. However, research in these in vitro model studies could reduce the use of animals. This is favored with the use of future technologies such as 3D bioprinting or organ-on-a-chip technologies.

Gasdermin E promotes translocation of p65 and c-jun into nucleus in keratinocytes for progression of psoriatic skin inflammation

Gasdermin E (GSDME) has recently been identified as a critical executioner to mediate pyroptosis. While epidermal keratinocytes can initiate GSDME-mediated pyroptosis, the role of keratinocyte GSDME in psoriatic dermatitis remains poorly characterized. Through analysis of GEO datasets, we found elevated GSDME levels in psoriatic lesional skin. Additionally, GSDME levels correlated with both psoriasis severity and response to biologics treatments. Single-cell RNA sequencing (scRNA-seq) from a GEO dataset revealed GSDME upregulation in keratinocytes of psoriasis patients. In the imiquimod (IMQ)-induced psoriasis-like dermatitis mouse model, both full-length and cleaved forms of caspase-3 and GSDME were elevated in the epidermis. Abnormal proliferation and differentiation of keratinocytes and dermatitis were attenuated in Gsdme-/- mice and keratinocyte-specific Gsdme conditional knockout mice after IMQ stimulation. Exposure of keratinocytes to mixed cytokines (M5), mimicking psoriatic conditions, led to GSDME cleavage. Moreover, the interaction between GSDME-FL and p65 or c-jun was significantly increased after M5 stimulation. GSDME knockdown inhibited nuclear translocation of p65 and c-jun and decreased upregulation of psoriatic inflammatory mediators such as IL1β, CCL20, CXCL1, CXCL8, S100A8, and S100A9 in M5-challenged keratinocytes. In conclusion, GSDME in keratinocytes contributes to the pathogenesis and progression of psoriasis, potentially in a pyroptosis-independent manner by interacting and promoting translocation of p65 and c-jun. These findings suggest that keratinocyte GSDME could serve as a potential therapeutic target for psoriasis treatment.

Human Skin Drug Metabolism: Relationships between Methyl Salicylate Metabolism and Esterase Activities in IVPT Skin Membranes

The presence of esterase enzymes in human skin and their role in drug metabolism has been reported, but their distribution in the various skin layers and the relative contributions of those layers to metabolism is poorly defined. To gain further insight into esterase distribution, we performed in vitro skin permeation of a commercial 28.3% methyl salicylate (MeSA) cream (Metsal™) in Franz diffusion cells, using a range of human skin membranes, all from the same donor. The membranes were viable epidermis separated by a dispase II enzymatic method, heat separated epidermis, dermatomed skin, and dermis separated by a dispase II enzymatic method. Methyl salicylate and its metabolite, salicylic acid (SA), were measured by high-performance liquid chromatography. Alpha naphthyl acetate and Hematoxylin and Eosin staining provided qualitative estimations of esterase distribution in these membranes. The permeation of methyl salicylate after 24 h was similar across all membranes. Salicylic acid formation and permeation were found to be similar in dermatomed skin and dermis, suggesting dermal esterase activity. These results were supported by the staining studies, which showed strong esterase activity in the dermal-epidermal junction region of the dermis. In contrast with high staining of esterase activity in the stratum corneum and viable epidermis, minimal stained and functional esterase activity was found in heat-separated and dispase II-prepared epidermal membranes. The results are consistent with dispase II digesting hemidesmosomes, penetrating the epidermis, and affecting epidermal esterases but not those in the dermis. Accordingly, whilst the resulting dispase II-generated dermal membranes may be used for in vitro permeation tests (IVPT) involving esterase-based metabolic studies, the dispase II-generated epidermal membranes are not suitable for this purpose.

N-eicosapentaenoyl-ethanolamine decreases the proliferation of psoriatic keratinocytes in a reconstructed psoriatic skin model

Psoriasis is an inflammatory skin disease that is characterized by keratinocyte hyperproliferation, abnormal epidermal differentiation and dysregulated lipid metabolism. Some lipid mediators of the N-acylethanolamines (NAEs) and monoacylglycerols (MAGs) can bind to cannabinoid (CB) receptors and are referred to as part of the endocannabinoidome. Their implication in psoriasis remains unknown. The aim of the present study was to characterize the endocannabinoid system and evaluate the effects of n-3-derived NAEs, namely N-eicosapentaenoyl-ethanolamine (EPEA), in psoriatic keratinocytes using a psoriatic skin model produced by tissue engineering, following the self-assembly method. Psoriatic skin substitutes had lower FAAH2 expression and higher MAGL, ABHD6 and ABHD12 expression compared with healthy skin substitutes. Treatments with alpha-linolenic acid (ALA) increased the levels of EPEA and 1/2-docosapentaenoyl-glycerol, showing that levels of n-3 polyunsaturated fatty acids modulate related NAE and MAG levels. Treatments of the psoriatic substitutes with 10 μM of EPEA for 7 days resulted in decreased epidermal thickness and number of Ki67 positive keratinocytes, both indicating decreased proliferation of psoriatic keratinocytes. EPEA effects on keratinocyte proliferation were inhibited by the CB₁ receptor antagonist rimonabant. Exogenous EPEA also diminished some inflammatory features of psoriasis. In summary, n-3-derived NAEs can reduce the psoriatic phenotype of a reconstructed psoriatic skin model.

Pathology and Treatment of Psoriasis Using Nanoformulations

Psoriasis (PSO) is an inflammatory skin condition that causes a variety of diseases and significantly decreases the life characteristics of patients, and substantially diminishes patients' quality of life. PSO usually impairs the skin and is linked to various disorders. Inflammation pathology does not only damage psoriatic skin; it shows how PSO impinges other body parts. Many variables interact with one another and can impact the etiology of psoriasis directly or indirectly. PSO has an effect on approximately 2% of the world's population, and significant progress has been made in comprehending and treating the alternative PSO by novel drug delivery systems. Topical, systemic, biological, biomaterials, and phototherapy are some of the useful therapies for PSO. Nonetheless, topical treatments remain the gold standard for treating moderate PSO. The applicability of several nanocarrier systems, such as lipid nanoparticles, metallic nanoparticles, and certain phytocompounds, has been briefly explored. The present review focuses mainly on traditional therapeutic strategies as well as on breakthroughs in nanoformulations and drug delivery methods for several anti-psoriatic drugs.

Gene Profiling of a 3D Psoriatic Skin Model Enriched in T Cells: Downregulation of PTPRM Promotes Keratinocyte Proliferation through Excessive ERK1/2 Signaling

Psoriasis is a complex, immune-mediated skin disease involving a wide range of epithelial and immune cells. The underlying mechanisms that govern the epidermal defects and immunological dysfunction observed in this condition remain largely unknown. In recent years, the emergence of new, more sophisticated models has allowed the evolution of our knowledge of the pathogenesis of psoriasis. The development of psoriatic skin biomaterials that more closely mimic native psoriatic skin provides advanced preclinical models that will prove relevant in predicting clinical outcomes. In this study, we used a tissue-engineered, two-layered (dermis and epidermis) human skin substitute enriched in T cells as a biomaterial to study both the cellular and molecular mechanisms involved in psoriasis’ pathogenesis. Gene profiling on microarrays revealed significant changes in the profile of genes expressed by the psoriatic skin substitutes compared with the healthy ones. Two genes, namely, PTPRM and NELL2, whose products influence the ERK1/2 signaling pathway have been identified as being deregulated in psoriatic substitutes. Deregulation of these genes supports excessive activation of the ERK1/2 pathway in psoriatic skin substitutes. Most importantly, electrophoresis mobility shift assays provided evidence that the DNA-binding properties of two downstream nuclear targets of ERK1/2, both the NF-κB and Sp1 transcription factors, are increased under psoriatic conditions. Moreover, the results obtained with the inhibition of RSK, a downstream effector of ERK1/2, supported the therapeutic potential of inhibiting this signaling pathway for psoriasis treatment. In conclusion, this two-layered human psoriatic skin substitute enriched in T cells may prove particularly useful in deciphering the mechanistic details of psoriatic pathogenesis and provide a relevant biomaterial for the study of potential therapeutic targets.

Current knowledge of the implication of lipid mediators in psoriasis

The skin is an organ involved in several biological processes essential to the proper functioning of the organism. One of these essential biological functions of the skin is its barrier function, mediated notably by the lipids of the stratum corneum, and which prevents both penetration from external aggression, and transepidermal water loss. Bioactive lipid mediators derived from polyunsaturated fatty acids (PUFAs) constitute a complex bioactive lipid network greatly involved in skin homeostasis. Bioactive lipid mediators derived from n-3 and n-6 PUFAs have well-documented anti- and pro-inflammatory properties and are recognized as playing numerous and complex roles in the behavior of diverse skin diseases, including psoriasis. Psoriasis is an inflammatory autoimmune disease with many comorbidities and is associated with enhanced levels of pro-inflammatory lipid mediators. Studies have shown that a high intake of n-3 PUFAs can influence the development and progression of psoriasis, mainly by reducing the severity and frequency of psoriatic plaques. Herein, we provide an overview of the differential effects of n-3 and n-6 PUFA lipid mediators, including prostanoids, hydroxy-fatty acids, leukotrienes, specialized pro-resolving mediators, N-acylethanolamines, monoacylglycerols and endocannabinoids. This review summarizes current findings on lipid mediators playing a role in the skin and their potential as therapeutic targets for psoriatic patients.

Antipsoriatic Potential of Quebecol and Its Derivatives

Psoriasis is a chronic inflammatory skin disease mainly characterized by the hyperproliferation and abnormal differentiation of the epidermal keratinocytes. An interesting phenolic compound, namely quebecol (2,3,3-tri-(3-methoxy-4-hydroxyphenyl)-1-propanol) (compound 1, CPD1), was isolated from maple syrup in 2011 and was recently synthesized. Quebecol and its derivatives ethyl 2,3,3-tris(3-hydroxy-4-methoxyphenyl)propenoate (compound 2, CPD2) and bis(4-hydroxy-3-methoxyphenyl)methane (compound 3, CPD3) have shown antiproliferative and anti-inflammatory potential, making them promising candidates for the treatment of psoriasis. This study aimed to evaluate the antipsoriatic potential of quebecol and its derivatives on psoriatic skin substitutes produced according to the self-assembly method. A sulforhodamine B (SRB) assay determining the concentration that inhibits 20% of cell growth (IC20) was performed for CPD1, CPD2 and CPD3, and their IC20 values were 400, 150 and 350 μM, respectively. At these concentrations, cell viability was 97%, 94% and 97%, respectively. The comparative control methotrexate (MTX) had a cell viability of 85% at a concentration of 734 μM. Histological analyses of psoriatic skin substitutes treated with CPD1, CPD2 and CPD3 exhibited significantly reduced epidermal thickness compared with untreated psoriatic substitutes, which agreed with a decrease in keratinocyte proliferation as shown by Ki67 immunofluorescence staining. The immunofluorescence staining of differentiation markers (keratin 14, involucrin and loricrin) showed improved epidermal differentiation. Taken together, these results highlight the promising potential of quebecol and its derivatives for the treatment of psoriasis.

Docosahexaenoic Acid Modulates Paracellular Absorption of Testosterone and Claudin-1 Expression in a Tissue-Engineered Skin Model

Healthy skin moLEdels produced by tissue-engineering often present a suboptimal skin barrier function as compared with normal human skin. Moreover, skin substitutes reconstructed according to the self-assembly method were found to be deficient in polyunsaturated fatty acids (PUFAs). Therefore, in this study, we investigated the effects of a supplementation of the culture media with docosahexaenoic acid (DHA) on the barrier function of skin substitutes. To this end, 10 μM DHA-supplemented skin substitutes were produced (n = 3), analyzed, and compared with controls (substitutes without supplementation). A Franz cell diffusion system, followed by ultra-performance liquid chromatography, was used to perform a skin permeability to testosterone assay. We then used gas chromatography to quantify the PUFAs found in the epidermal phospholipid fraction of the skin substitutes, which showed successful DHA incorporation. The permeability to testosterone was decreased following DHA supplementation and the lipid profile was improved. Differences in the expression of the tight junction (TJ) proteins claudin-1, claudin-4, occludin, and TJ protein-1 were observed, principally a significant increase in claudin-1 expression, which was furthermore confirmed by Western blot analyses. In conclusion, these results confirm that the DHA supplementation of cell culture media modulates different aspects of skin barrier function in vitro and reflects the importance of n-3 PUFAs regarding the lipid metabolism in keratinocytes.

Development of a 3D psoriatic skin model optimized for infiltration of IL-17A producing T cells: Focus on the crosstalk between T cells and psoriatic keratinocytes

Psoriasis is a chronic inflammatory skin disease involving several cell types, including T cells, via the IL-23/IL-17 axis. IL-17A acts on the surrounding epithelial cells thus resulting in an inflammatory feedback loop. The development of immunocompetent models that correctly recapitulate the complex phenotype of psoriasis remains challenging, which also includes both the T cell isolation and activation methods. The purpose of this work was to develop an advanced in vitro 3D psoriatic skin model that enables the study of the impact of T cells on psoriatic epithelial cells. To reach that aim, healthy and psoriatic fibroblasts and keratinocytes were used to reproduce this tissue-engineered skin model in which activated T cells, isolated beforehand from human whole blood, have been incorporated. Our study showed that isolation of T cells with the EasySep procedure, followed by activation with PMA/ionomycin, mimicked the psoriatic characteristics in an optimal manner with the production of inflammatory cytokines important in the pathogenesis of psoriasis, as well as increased expression of Ki67, S100A7, elafin and involucrin. This psoriatic model enriched in activated T cells displayed enhanced production of IL-17A, IFN-ƴ, CCL2, CXCL10, IL-1ra, IL-6 and CXCL8 compared with the healthy model and whose increased secretion was maintained over time. In addition, anti-IL17A treatment restored some psoriatic features, including epidermal thickness and basal keratinocytes proliferation, as well as a downregulation of S100A7, elafin and involucrin expression. Altogether, our study demonstrated that this model reflects a proper psoriatic inflammatory environment and is effective for the investigation of epidermal and T cell interaction over time. STATEMENT OF SIGNIFICANCE: The aim of this study was to provide an innovative 3D immunocompetent human psoriatic skin model. To our knowledge, this is the first immunocompetent model that uses skin cells from psoriatic patients to study the impact of IL-17A on pathological cells. Through the use of this model, we demonstrated that the T-cell enriched psoriatic model differs from T-cell enriched healthy model, highlighting efficient crosstalk between pathologic epithelial cells and T cells. This advanced preclinical model further mimics the original psoriatic skin and will prove relevant in predicting clinical outcomes, thereby decreasing inaccurate predictions of compound effects.

Investigation of Omega-3 Polyunsaturated Fatty Acid Biological Activity in a Tissue-Engineered Skin Model Involving Psoriatic Cells

Clinical studies have shown that diets enriched with omega-3 (also know as n-3) polyunsaturated fatty acids could relieve the symptoms of patients with psoriasis. However, the mechanisms involved remain poorly understood. The aim of this study was to investigate the effects of α-linolenic acid (ALA) on the proliferation and differentiation of psoriatic keratinocytes in a three-dimensional skin model. Skin models featuring healthy (healthy substitute) or psoriatic (psoriatic substitute) cells were engineered by the self-assembly method of tissue engineering using a culture medium supplemented with 10 μM ALA in comparison with the regular unsupplemented medium. ALA decreased keratinocyte proliferation and improved psoriatic substitute epidermal differentiation, as measured by decreased Ki67 staining and increased protein expression of FLG and loricrin. The added ALA was notably incorporated into the epidermal phospholipids and metabolized into long-chain n-3 polyunsaturated fatty acids, mainly eicosapentaenoic acid and n-3 docosapentaenoic acid. ALA supplementation led to increased levels of eicosapentaenoic acid derivatives (15-hydroxyeicosapentaenoic acid and 18-hydroxyeicosapentaenoic acid) as well as a decrease in levels of omega-6 (also know as n-6) polyunsaturated fatty acid lipid mediators (9-hydroxyoctadecadienoic acid, 12-hydroxyeicosatetraenoic acid, and leukotriene B₄). Furthermore, the signal transduction mediators extracellular signal‒regulated kinases 1 and 2 were the kinases most activated after ALA supplementation. Taken together, these results show that ALA decreases the pathologic phenotype of psoriatic substitutes by normalizing keratinocyte proliferation and differentiation in vitro.